Electronic timers are indispensable in many electronics applications, especially those involving digital communications. In many digital wireless communication systems, for example, a mobile station (MS) that communicates with a base station must be synchronized to the timing of the base station to ensure that the MS will receive all signals addressed to it. Typically, a high frequency oscillator in the MS drives a timing circuit that monitors the received radio-frequency (RF) channels at appointed times for control signals from the base station. Conventional wireless stations require the high frequency oscillator and the timing circuitry to operate almost constantly, even when the MS is in sleep mode, during which power is removed from the receiver circuitry to extend the life of the station's power supply. This is true even though the MS, while in sleep mode, must be active only for short, predetermined time periods to receive paging signals from the base station. In a global system for mobile (GSM) network, for example, the MS may remain in sleep mode for all but 18.5 ms during each time period of 2.2 seconds.
In a typical MS, the high frequency timing circuitry consumes a relatively large portion of the power provided by the station's power supply, often exceeded only by the power consumed by the receiver circuitry. Because a MS may spend most of its time in sleep mode, the high frequency timing circuitry often is the most critical component in determining the life of the station's power supply.